The present technology relates to an image signal processor, an image signal processing method, and a program for correcting a flicker of an image signal.
An image sensor accumulates electric charge at a different point in time depending on each surface or line. In general, a so-called global-shutter-type image sensor selects when to accumulate electric charge of each surface. A so-called rolling-shutter-type image sensor selects when to accumulate electric charge of each line. In the past, global-shutter-type CCD image sensors have been used mainly. However, in recent years, CMOS image sensors are the focus of attention. A CMOS image sensor uses less power than a CCD image sensor does. The number of components of a CMOS image sensor is smaller than that of a CCD image sensor. The manufacturing cost of a CMOS image sensor is smaller than that of a CCD image sensor. Most CMOS image sensors are rolling-shutter type because of structural difficulties. In both the types, when an image is taken with a blinking light source, contrast is found in surfaces (surface flicker) or contrast is found in lines (line flicker) depending on a point of time at which a sensor accumulates electric charge.
As a technology of correcting a flicker, there is known a method of approximating the phase and amplitude of a flicker to thereby generate a waveform such as a sine wave, and correcting a flicker of an image signal based on the waveform (see Japanese Patent Application Laid-open No. 2007-295200). This method has resistance to change of a level. Further, there is also known a method of calculating the arithmetic mean of integrated values of pixel values of each frame of the integral multiple of a flicker cycle to thereby generate a reference image from which a flicker component is removed, and correcting a flicker of an image signal by using the reference image (see Japanese Patent Application Laid-open No. 2000-324365). This method is vulnerable to change of a level, but its correction accuracy is high.